The present invention relates to a physical quantity distribution sensor, a method of driving said sensor and a method of producing said sensor.
Recently, there is increased a demand for a semiconductor device for sensing the spatial distribution of a physical quantity in a variety of fields. Particular attention is placed on a solid-state imaging device for sensing a light quantity as the physical quantity. More specifically, such a so-called amplifier-type solid-state imaging device is designed in the following manner. A plurality of storage sections are arranged to store a signal electric charge obtained through photo-electric conversion at the associated one of a plurality of photoelectric conversion sections. Each storage section is connected to the operation control portion of a transistor such as the gate of a field-effect transistor (FET) or the base of a bipolar transistor, or provision is made such that the storage section also serves as an operation control section. Accordingly, an electric current flowing in each transistor is controlled based on that potential of the associated storage section which varies with the amount of a signal electric charge.
With reference to FIG. 12, the following description will discuss the arrangement and operation of a physical quantity distribution sensor of prior art with an amplifier-type solid-state imaging device taken as an example.
As shown in FIG. 12, pixels 2 are arranged in a plurality of rows and a plurality of columns in an imaging region (generally, a region in which a physical quantity is to be sensed and stored) 1. Each pixel 2 comprises a photoelectric conversion/storage section 3 and a driving transistor 5 having a gate 4.
A selected-row-driving transistor 10 is disposed in each selected-row-driver 8, and a voltage is to be supplied to each selected-row-driving transistor 10 from a selected-row-driving-voltage input portion 9. Whether or not each selected-row-driving transistor 10 is electrically conductive, is controlled by a voltage of each output portion 7 of a shift register for row selection 6. An output of a selected-row-driving transistor 10 is connected to a plurality of row-select-transistors 12 arranged in the row through one of row selection lines 11, which allows a single pixel row to be selected out of the plurality of pixel rows.
The row-select-transistors 12 arranged in the same column are connected to a corresponding one of load transistors 14 through one of vertical signal lines 13. The output potential of each photoelectric conversion/storage section 3 varies with the amount of signal electric charge stored therein. The output potential of each photoelectric conversion/storage section 3 is given to the gate 4 of a corresponding driving transistor 5 which is connected to one of power supply lines 17. There is formed a source follower circuit in which the driving transistor 5 serves as a driving transistor and in which the load transistor 14 connected to a second power supply voltage (Vss) terminal 15 and to a gate input portion 16, serves as a load transistor. A power supply voltage (Vdd) is supplied to each power supply line 17 from a first power supply voltage (Vdd) terminal 27.
An output of the source follower circuit including the driving transistor 5 and the load transistor 14 is supplied to one of horizontal signal lines 24 through a signal column selection transistor 23 disposed in the associated one of column selection drivers 22. Whether or not signal column selection transistors 23 are electrically conductive, is controlled by voltages generated at output portions 21 of a shift register 20 for column selection. According to this control, a single pixel column is selected out of the plurality of pixel columns. An output of the source follower circuit in a selected column, is selectively sent to an impedance conversion section 25 through the horizontal signal line 24, and then supplied to an output portion 26 through the impedance conversion section 25.
After the signals are read out from all the pixels 2 arranged in the selected row, a reset voltage input portion 28 sends a reset voltage to the selected-row-reset-driving transistor 29 in the selected-row-driver 8 for the selected row, thereby to drive the pixel reset transistors 30 in the selected row through a pixel-reset-voltage-supply line 19 associated with the selected row. This resets the signal electric charges stored in the photoelectric conversion/storage sections 3 in the selected row. Then, these photoelectric conversion/storage sections 3 again start storing signal electric charges.
According to the above-mentioned arrangement of prior art, each pixel has a photoelectric conversion section and an electric charge storage section, or a photoelectric conversion/storage section 3 having both conversion and storage functions as in the above example, a row-select-transistor 12, a driving transistor 5 for amplifying an output of the photoelectric conversion/storage section 3, and a reset transistor 30 for resetting the electric charge stored in the electric charge storage section or the photoelectric conversion/storage section 3. Further, there are required a number of input/output lines such as the power supply lines 17 for driving transistors, the row-select-lines 11, the pixel-reset-voltage-supply lines 19, the vertical signal lines 13 and the like.
This complicates each pixel in arrangement and makes it difficult to enhance the performance thereof. It is also difficult to reduce each pixel in area to increase the number of pixels in the same area and to reduce the device in size.
In view of the foregoing, it is an object of the present invention to provide a physical quantity distribution sensor reduced in the number of input lines connected to pixels to simplify the pixels in arrangement, thus enabling to increase the number of pixels in the same area and to reduce the device in size.